Guild Wars 2

You do a couple missions for each order first, then you can choose

For a norn, here are the two possible personal story steps where you select an order:
http://wiki.guildwars2.com/wiki/Sabotage
http://wiki.guildwars2.com/wiki/Code_Breaker

Make sure you’re at one of those story steps, have performed all the listed objectives, and spoken to Eir once you’ve completed the objectives, then you should get the option to select your order.

And, of course, look at the quest tracker in the top right of your screen. It will tell you what you need to do next.

You’re not at the point where you can choose a faction permanently yet. If you are, Eir will explicitly tell you so.